https://medium.com/citizen-truth/are-apps-tracking-you-even-after-you-uninstall-them-140ea8cfffd2

Many app developers now track users even after users have uninstalled their apps, and the tracking allows companies to continue to serve targeted ads. Bloomberg first reported on this new phenomenon of “uninstall tracking.” With uninstall tracking you are never completely free from unwanted mobile apps, because the owner companies can still monitor you around the web.

A new industry of companies offer uninstall tracking as part of larger app development services. The companies claim the tracking allows app developers to measure how customers react to app updates; however, tracking a person after they have uninstalled your app could be seen as an invasion of privacy.